Layered video multicast transmission system with retransmission-based error recovery

1. A real-time, layered video multicast transmission system for transmitting video frames as a stream of encoded video data packets from a sender to one or more receivers over a network, wherein there exists a defined amount of time to recover lost packets said system comprising: means for generating one or more independent layers of video substreams out of said encoded video stream, each said one or more receivers capable of subscribing to one or more layers of said independent video substreams; means for transporting each of said independent video substreams over said network, said transporting means transporting each substream as an independent flow capable of being received by each said one or more receivers; control means for monitoring congestive state of said receiver to determine said receiver's capability for receiving each said video substream layer, said receiver selecting one or more of said independent video streams in accordance with the congestive state of said receiver wherein the system further comprising adaptive playback control means for extending said amount of time to recover packets lost during transport.

2. A real-time layered video multicast transmission system as claimed in claim 1, wherein said control means provides hierarchical rate control.

3. A real-time layered video multicast transmission system as claimed in claim 1, further comprising means provided in each layer for effecting retransmission of packets lost during transport of each frame.

4. A real-time layered video multicast transmission system as claimed in claim 1, wherein said adaptive playback control enables recovery within said amount of time based on amount of video substream layers subscribed to by said receiver.

5. A real-time layered video multicast transmission system as claimed in claim 1, wherein said means for generating one or more independent video substreams out of said encoded video stream includes a demultiplexer.

6. A real-time layered video multicast transmission system as claimed in claim 1, further including means located at said receiver for generating a video frame out of one or more independent video streams received.

7. A real-time layered video multicast transmission system as claimed in claim 1, wherein said layered video multicast is MPEG video, said independent video substream constituting one of I, P or B frames of said MPEG video.

8. A real-time layered video multicast transmission system as claimed in claim 1, wherein said means for transporting each of said independent video substreams over said network includes separate transport devices and a designated transport leader device.

9. A real-time layered video multicast transmission system as claimed in claim 1, wherein said said receiver state includes one of a unloaded, congested, and unloaded states, said control means including means for determining whether a receiver drops a video layer when in said congested state and adds a video layer when in said unloaded state.

10. A real-time layered video multicast transmission system as claimed in claim 1, wherein said receiver joins a multicast group when adding a video layer or leaves a multicast group when dropping a video layer.

11. A real-time layered video multicast transmission system as claimed in claim 10, wherein said control means places said receiver in an unstable state after said receiver either drops or adds a video layer.

12. A real-time layered video multicast transmission system as claimed in claim 9, wherein said control means includes means for determining a video packet loss rate for a receiver, said control means placing said receiver in a congested state when said packet loss rate exceeds a first predetermined threshold and placing said receiver in an unloaded state when said packet loss rate drops below a second predetermined threshold.

13. A method for transmitting video frames as a stream of encoded video data packets from a sender to one or more receivers over a network, wherein there exists a defined amount of time to recover lost packets comprising the steps of: generating one or more independent layers of video substreams out of said encoded video stream, each said one or more receivers subscribing to one or more layers of said independent video substreams; transporting each of said independent video substreams over said network, each independent video substream transported as an independent flow for receipt by each said one or more receivers; monitoring congestive state of said receiver to determine receiver's capability for receiving each said video substream layer; and enabling said receivers to select one or more of said independent video streams in accordance with the congestive state of said receiver said transport step further in the step of adaptively extending said amount of time to recover packets lost during transport.

14. A real-time, layered video multicast transmission system for transmitting a video frame as as one or more independent substream layers of encoded video data packets from a sender to one or more receivers over a network, each said one or more receivers capable of subscribing to one or more said independent layers, said system comprising: control means for monitoring congestive state of said receiver to determine said receiver's capability for receiving each said video substream layer, said receiver selecting one or more of said independent substreams in accordance with the congestive state of said receiver, means implemented in said receiver for generating a retransmission request for lost packets in a received video frame, said sender capable of retransmitting said lost video packets within an amount of time before arrival of packets belonging to a next video frame; and, adaptive playback control means for extending said amount of time to recover said lost packets in accordance with said congestive state of said receiver to thereby improve video transmission quality.

15. A real-time, layered video multicast transmission system as claimed in claim 14 for wherein said adaptive playback control means extends said amount of time to recover said lost packets based on amount of video substream layers subscribed to by said receiver.